It has been known for a number of years that the rewarding effects of electrical stimulation of the lateral hypothalamus involve the ascending dopamine systems to the forebrain. However, we do not have a clear idea as to the relative involvement of the various terminal fields of the dopamine systems in this reward effect. We propose to map the relative involvement of each dopamine terminal field by injecting each terminal structure one at a time with a dopamine receptor blocker, Alpha-flupenthixol. The amount of degradation occurring in the pulse effectiveness of rewarding hypothalamic stimulation will then be determined using recently developed quantitative measurement techniques. We will then extend these observations to the chronic state by making similar injections of the neurotoxin, 6-OHDA. This will enable us to examine and scale the extent of recovery from selective destruction of dopamine terminals and to localize the cells of origin by examining with histofluorescence methods the cell loss within the A9-A10 area. Finally, a more precise neuroanatomical localization of the dopamine cells involved in rewarding hypothalamic stimulation will be conducted using retrograde fluorescent double labelling techniques. This is an important phase of the project since it is likely that more than one dopamine terminal field contributes to these reward effects. Therefore the double-labelling experiments will reveal whether functionally similar (e.e. reward) terminal structures are innervated by the same dopamine neurons, that is, neurons that branch to innervate two different terminal structures.